Global Warming

One would think after all this time, with the subject being discussed or mentioned daily in the papers and on TV, that everyone would understand what it’s all about. Surprisingly, not true. The whole subject, existentially catastrophic as it clearly is, has been politicized. I am no recognized authority, but it only takes a person moderately informed and schooled in simple science to lay out what are the settled facts.

Science agrees life probably appears on any star’s planets that happen to be circling in the ‘Goldilocks’ zone, that region where water is liquid. There are three such planets in our system; Venus, Earth, and Mars. We live on the lucky one. Evidence shows that in the early days Venus, Earth’s twin, probably had oceans. The same with Mars. Runaway Greenhouse effect occurred on Venus and now it has no water, the surface temperature is equal to that of molten lead, and the surface atmospheric pressure is 50 times that of Earth. Mars could have fared better but it was a bit too small and had insufficient gravity to hold an atmosphere (currently about 1% of Earth’s pressure). In addition the lack of a moderately strong magnetic field such as that of the Earth’s allowed solar winds of high energy particles to sweep way the top layers of the atmosphere. If it were bigger and had a layer of Greenhouse gas it might have maintained the oceans it once had and could have been a pretty nice place.

Science estimates there may be as many as one trillion galaxies in the universe, each with from 100 to 400 billion stars and each star home to a number of planets. Not all planets would be in the liquid water zone but at least a few trillion would be. There is sadly a fateful story that goes with these possible habitations. Stars get old, increase their radiative output, and eventually swell up and actually devour all these cozy inner planets. Not to worry though. Our sun has a few billion years to go before we are burned to a crisp.

Part of our difficulty in dealing with the problem has to do with our sense of time and number. Most of us are just beginning to get a grasp of a million. Say a moderately successful person makes $100,000 a year. One million dollars is ten years wages. That person would need to work at that salary for 10,000 years to earn one billion dollars. The Great Lakes came into being about 12,000 years ago, a minuscule flash of time in the geological scale. Arctic and Antarctic ice is currently melting at a blindingly rapid rate.

We know what causes greenhouse warming, primarily excesses of CO2 and methane. Methane is approximately 200 times more effective at trapping heat on the Earth’s surface than CO2 but it is CO2 that has pulled the trigger. Methane is the principal ingredient of natural gas. We have all seen flames of burning methane spouting from stacks associated with oil wells. It is generally uneconomic to capture and market it and as is obvious from its greenhouse effect it cannot be released into the air. Better to convert its ingredients to CO2. The topic of methane’s role in global warming is under study. There are a small number of scientists who disagree on methane’s hazardous effect. The worry is that the vast quantities of methane that are frozen into the arctic tundra and exist at the bottom of the colder oceans as ‘methrates,’ a solid icy form of methane, could be released into the atmosphere with the warming of the oceans and the thawing of the tundra.

These dire facts remind me of a remark I heard at a cocktail gathering at the US Grant Hotel in San Diego several decades ago. Roger Revelle, eminent oceanographer, author of much of the global warming data, and founder of UCSD, and the President of SDSU,  Tom Day, were chatting. Revelle remarked that we were doing this gigantic experiment involving the whole Earth and alarmingly we had only this one planet and no idea how this experiment would turn out.

Effects of very small increases in average temperature planet wide include rises in sea level caused by swelling of the water. There are however drastic differences in yearly temperatures in the polar regions compared to the lower latitudes. Polar ice is melting at six times the rate earlier estimated. Warmer oceans result in a reduction of food supply at the bottom of the food chain. I guess I needn’t mention typhoons, hurricanes, tornadoes, floods, and wildfires in the dry areas. 

What are the simple physics explanations of global warming? This is a topic seldom dealt with in the popular press even though the basic ideas are accessible to any normal person. The sun radiates its energy across the spectrum from the ultraviolet to the infrared but most of the sun’s energy is heaped up in the region from the near ultraviolet through the visible to the near infrared. Its distribution is very much like that of a black body heated to about 6000 degrees Kelvin. The largest share of the energy is in what we normally think of as the optical region. It passes from the sun through our atmosphere with little impedance and is absorbed by the water, the land, and whatever else is illuminated. Most of these surfaces have a lower reflectivity than 100% so much of the radiation is absorbed and converted to heat – the temperature of the surface rises. There has to be a balance – what comes in has to be radiated out at some point so the surface gets hotter and hotter till its own blackbody radiation equals what it its receiving. This radiation however is not in the optical region. It is in the far infrared.

 

Greenhouse gasses in the atmosphere have a molecular structure that makes them prone to absorb the heat rays from the surface instead of passing them through to outer space. These gasses do emit their absorbed radiation but they emit it in all directions including back down to the surface. The incoming radiation came straight through and any reflected radiation in the optical region goes straight out.  But about half of the absorbed radiation never gets out. In some instances this might be a desirable effect. It would mean that somewhat cold planets could be warmed up through the presence of a limited amount of greenhouse gasses. In other instances, such as with our own planet, there is a runaway effect – increased temperatures will affect the uptake of CO2 sequestering mechanisms. This is especially true of the polar regions and the vast forested areas that may be denuded by the warming trend and wildfires such as are occurring in Brazil. It is crucial to understand that trees are the key. Grass and crops do not replace the beneficial effects of trees.

The argument is made that water and other gasses in the atmosphere also have a greenhouse effect. That is true but it's a matter of balance. An excess of any of these agents can tip the balance.  Currently the human population of the Earth, about 7.6 billion, contributes 24 billion tons of CO2 to the air through industrial and other fossil fuel expenditures.. To maintain a balance it is estimated that normal human activity might be managed at a much lower amount. There is a normal carbon cycle in the natural Earth's processes. The amounts of carbon in this cycle may seem quite large in comparison to the quantities cited above but the crucial factor is balance. It apparently takes only a very small fraction to upset this cycle.

Keep in mind that without life there is no oxygen. There was a time when the Earth’s atmosphere did not have oxygen in it. Plants, in the ocean primarily, put it there. Carbon was sequestered hundreds of millions of years ago in vast amounts as oil and coal. Now we are digging it all up and putting it back into the air and water. There is enough oil and coal in the ground – easily accessible – to kill the planet dead many times over. Sequestration is the ultimate answer. CO2 can be sequestered in the oceans to a certain degree. Beyond that the oceans become more acidic. Coral dies. Other vital life forms disappear.

People often cite volcanoes as a  major source of CO2. An article in Scientific American points out that volcanic activity (200 million tons) contributes less than 1% of that contributed by human activity - 24 Billion tons per year.

What can we do about all this? Here are a few things that are being done or have been proposed. It’s all pretty small peanuts so far.

1)     *   Quit using so much fossil fuel.

2)     *   Develop safe nuclear energy.

3)      * Put the CO2 back in the ground.

4)      * Sprinkle iron on the oceans to promote formation of plankton with carbonate shells.

5)      * Put a cloud of reflectors in space.

6)       *   Convert the CO2 to useful solid carbon industrial products.

7)      * Reforest several billion hectares of forest (Yes, the land is available


IIn response to the many global warming deniers around, and there are plenty of them, have them take a look at the latest map of Greenland that shows all the new coastal topography and islands that have been revealed by the melting of that icecap in the last few years.